Preparation of low molecular weight copolymer salts

Abstract

A method for forming ionic copolymer salts from low molecular weight copolymer acids formed from ethylene and an alpha,beta-ethylenically unsaturated carboxylic acid having at least one carboxylic acid group, and cations having a valence of 1 to 3. The copolymer acid and the cation containing material are fed to a reaction vessel. The reaction vessel is maintained below atmospheric pressure, for at least a portion of the time, so that the oxygen content of the reaction vessel is minimized and volatile reaction products are removed. The reacting mixture is continually stirred or mixed within the reaction vessel. The temperature within the reaction vessel is controlled and maintained above the melting point of the polymer.

What is claimed is: 
     
       1. A method of making ionic copolymer salts from copolymer acids formed from ethylene and an alpha,beta-ethylenically unsaturated carboxylic acid having at least one carboxylic acid group, the copolymer acid having a number average molecular weight of from 500 to 5000, and at least 50 mol percent ethylene, the copolymer acid being neutralized by cations selected from a group having a valence of 1 to 3, comprising the steps of: feeding the copolymer acid and a cation containing material to a reacting vessel;   maintaining a vacuum in the reaction vessel;   mixing the reacting mixture within the reaction vessel; and   maintaining the temperature within the reaction vessel above the melting point of the copolymer acid.   
     
     
       2. The method as recited in claim 1 wherein the alpha,beta-ethylenically unsaturated carboxylic acid has 3 to 8 carbon atoms. 
     
     
       3. The method as recited in claim 1 wherein the copolymer acid has a number average molecular weight from 1,000 to 3000. 
     
     
       4. The method as recited in claim 3 wherein the alpha,beta-ethylenically unsaturated carboxylic acid is selected from the group consisting of acrylic acid, methacrylic acid, ethacrylic acid, maleic acid and fumaric acid. 
     
     
       5. The method as recited in claim 4 wherein the copolymer acid has at least 50 mol percent ethylene. 
     
     
       6. The method as recited in claim 5 wherein the copolymer acid has at least 75 mol percent ethylene. 
     
     
       7. The method as recited in claim 6 wherein the copolymer acid has from 80 to 95 mol percent ethylene. 
     
     
       8. The method as recited in claim 1 wherein the cations are derived from a group of metals which are selected from Groups IA, IIA, IIIA and the transition elements of the Periodic Table of Elements. 
     
     
       9. The method as recited in claim 8 wherein the metal is selected from the group consisting of sodium, potassium, magnesium, calcium, barium, zinc and aluminum. 
     
     
       10. The method as recited in claims 3 or 9 wherein the cation containing material is selected from the group including metal: oxides, hydroxides, acetates, methoxides, ethoxides, nitrates, carbonates and bicarbonates. 
     
     
       11. The method as recited in claims 8 or 9 wherein the alpha,beta-ethylenically unsaturated carboxylic acid is acrylic acid. 
     
     
       12. The method as recited in claim 11 wherein from about 15% to about 60% of the carboxylic acid groups of the copolymer acid are neutralized. 
     
     
       13. The method as recited in claim 12 wherein from 25% to 50% of the carboxylic acid groups of the copolymer acid are neutralized. 
     
     
       14. The method as recited in claim 12 wherein the metal cation is the cation of calcium. 
     
     
       15. The method as recited in claim 14 wherein the cation containing material is calcium hydroxide. 
     
     
       16. The method as recited in claim 11 wherein the cation containing material is selected from a group consisting of Ca(OH) 2 , Ca(C 2  H 3  O 2 ) 2 , MgO, NaOH and Zn(C 2  H 3  O 2 ) 2 . 
     
     
       17. The method as recited in claim 11 wherein the copolymer of ethylene and acrylic acid has an acid number from about 1 to about 180. 
     
     
       18. The method as recited in claim 17 wherein the copolymer of ethylene and acrylic acid has an acid number from about 40 to about 160. 
     
     
       19. The method as recited in claim 18 wherein the copolymer of ethylene and acrylic acid has an acid number from about 40 to about 120. 
     
     
       20. The method as recited in claim 11 wherein the cation containing material is selected from the group including metal: oxides, hydroxides, acetates, methoxides, ethoxides, nitrates, carbonates and bicarbonates. 
     
     
       21. A method of making ionic copolymer salts from copolymer acids formed from ethylene and an alpha,beta-ethylenically unsaturated carboxylic acid having at least one carboxylic acid group, the copolymer acid having a number average molecular weight of from 500 to 5000, and at least 50 mol percent ethylene, the copolymer acid being neutralized by cations selected from a group having a valence of 1 to 3, comprising the steps of: feeding the copolymer acid and a cation containing material to a reaction vessel;   conducting the reaction for at least one-half hour of reaction time;   maintaining a reduced pressure in the reaction vessel from 15 to 29.9 inches of mercury for at least a portion of the reaction time;   maintaining the temperature in the reaction vessel from about 120° C. to about 300° C.; and   mixing the reacting mixture within the reaction vessel.   
     
     
       22. The method as recited in claim 21 further comprising the step of heating the reaction temperature to from 120° C. to 300° C. after the feeding step. 
     
     
       23. The method as recited in claim 21 further comprising the step of maintaining an inert atmosphere within the reaction vessel. 
     
     
       24. The method as recited in claim 23 wherein the inert atmosphere is nitrogen. 
     
     
       25. The method as recited in claims 21 or 24 wherein the alpha,beta-ethylenically unsaturated carboxylic acid is selected from the group consisting of acrylic acid and methacrylic acid. 
     
     
       26. The method as recited in claim 25 wherein the alpha,beta-ethylenically unsaturated carboxylic acid is acrylic acid. 
     
     
       27. The method as recited in claim 25 wherein the copolymer acid has a number average molecular weight from 1,000 to 3000. 
     
     
       28. The method as recited in claim 26 wherein the copolymer acid has from 80 to 95 mol percent ethylene. 
     
     
       29. The method as recited in claim 26 wherein from about 15% to about 60% of the carboxylic acid groups of the copolymer acid are neutralized. 
     
     
       30. The method as recited in claim 29 wherein from 25% to 50% of the carboxylic acid groups of the copolymer acid are neutralized. 
     
     
       31. The method as recited in claim 25 wherein the cations are derived from a metal selected from the group consisting of sodium, potassium, magnesium, calcium, barium, zinc and aluminum. 
     
     
       32. The method as recited in claim 31 wherein the reaction time is maintained from 1 hour to about 5 hours. 
     
     
       33. The method as recited in claim 32 wherein the reaction vessel is heated to from about 140° C. to about 260° C. and maintained at from 140° C. to about 260° C. 
     
     
       34. The method as recited in claim 33 wherein the reaction vessel is heated to from 180° C. to 220° C. and maintained at from 180° C. to 220° C. 
     
     
       35. The method as recited in claim 32 wherein the reduced pressure is maintained from 15 to 29.9 inches of mercury for at least 10 minutes of the last half of the reaction time. 
     
     
       36. The method as recited in claim 35 wherein the reduced pressure is from 20 to 28 inches of mercury. 
     
     
       37. The method as recited in claim 36 wherein the reduced pressure is from 24 to 26 inches of mercury. 
     
     
       38. The method as recited in claim 35 wherein the reduced pressure is maintained for at least 10 minutes of the last hour of reaction time. 
     
     
       39. The method as recited in claim 21 wherein: the reaction time is from 2 to 4 hours;   the reaction vessel is heated to 180° C. to 220° C.;   the reaction vessel is maintained at 180° C. to 220° C.; and   the pressure in the reaction vessel is reduced for from 10 minutes to 45 minutes during the last hour of reaction time.